export {}

// let arr: number[] = [1,2,3,4,5,6,7]
// arr.push(9)

let arr: (number | string)[] = [1, 'a', 2, 'b']

// 类型别名  type 类型别名 = 具体类型

type CustomArr = (number | string | boolean)[]

let arr1: CustomArr = [1,'a', false]
let arr2: CustomArr = [1,'b', true]